1. Technical Field
The present invention relates to an ink set and a droplet ejection apparatus using the ink set.
2. Related Art
Hitherto, inks containing pigments or dyes as coloring materials have been known. Pigment inks containing pigments as coloring materials are particularly preferably used for recording letters and the like due to the fact they have little bleeding and favorable water resistance and light resistance. Further, dye inks containing dyes as coloring materials are particularly preferably used for recording images and the like due to the fact they have favorable glossiness and color development, as well as vivid colors.
When the pigment ink and the dye ink provided with the above-described characteristics are used together, the recording quality of both the letters and images recorded on a recording medium becomes excellent. For this reason, in recent years, ink sets provided with both pigment ink and dye ink have been widely used.
Here, when an ink set provided with the pigment ink and the dye ink is applied to an ink jet recording apparatus, there are times when the pigment ink and the dye ink are mixed together at a nozzle surface provided with nozzle holes for ejecting ink. In such a case, there are times when the dispersion of the pigments in the pigment ink is disrupted by the dye ink and the pigments become aggregated. In particular, when the nozzle surface is cleaned by a wiping member provided for cleaning the nozzle surface, there have been times when the nozzle holes are blocked by the aggregations of pigment and the ejection stability of the ink is deteriorated. Further, defects have been generated in which the aggregations of pigments attached to the nozzle surface fall onto the recording medium.
In order to reduce this kind of pigment aggregation, JP-A-2010-84136 discloses adding a polymer having a lactam structure to the dye ink. Further, JP-A-2006-2094 discloses regulating the amount of counter-ions included in the pigment ink and dye ink.
However, in the above-described techniques of the related art, when the pigment ink and the dye ink were mixed together, it was not possible to sufficiently suppress the disruption of the pigment dispersion and there were times when aggregation of the pigments occurred. In particular, when using dye ink containing specific dyes refined in order to improve characteristics such as weather resistance (for example, light resistance and gas resistance), if the dye ink and pigment ink were mixed together, there were times when the dispersion of the pigments was remarkably deteriorated.